This invention relates to a tape cassette for tape printers, and more particularly, to a tape cassette having a cassette case with a film tape spool and an ink ribbon spool therein, a feed path for ribbons and film tapes of differing widths, and guiding members for the ribbons and tapes.
Various types of tape cassette to be employed in a tape printer have been proposed. A modern tape printer cassette generally includes a film tape as the printing medium and an ink ribbon provided within a cassette case. Often, the cassette case includes an upper case portion and a lower case portion, joined to form the cassette; images are printed on the film tape using an ink ribbon by means of a thermal head provided in a tape printer.
In these tape cassettes, the height of the outer wall of the lower case and the height of the ink ribbon guide are generally the same, and the same as the width of the ink ribbon therein. Consequently, if an ink ribbon employed in a cassette has sufficient width to cover various film tape widths, the height of the outer wall of the lower case, as well as the height of the ribbon guide, must necessarily increase. Conversely, if the height of the ribbon guide and the height of the outer wall of the lower case are lower than the ink ribbon width, the ink ribbon protrudes above of the ribbon guide and the outer wall, such that the joint surface of the upper and lower cases is adjacent the body of the ink ribbon. When the mating surfaces of the upper and lower cases of the cassette are adjacent the body of the ink ribbon, the think ink ribbon may be wrinkled or nipped when the upper and lower cases are joined. To combat this problem, the ribbon guide and lower case could be formed higher to corresponding to the ribbon width of the larger ribbon. It is, however, very difficult to resin-mold a high external wall all around the case, that is, a generally deep lower case, as the molding of deep, thin-walled shells is difficult.
With the conventional tape cassette, if the ink ribbon and the film tape are fed along the same feeding path to the thermal head, due to limited space available in the modern compact printer, the ink ribbon and the film tape are fed touching each other. If the film tape becomes rippled, the ink ribbon becomes rippled, causing images printed on the film tape to become blurred. In a tape cassette of the laminate type (a printed tape made by adhering a adhesive backing to a film tape after printing), if the film tape is drawn manually by a user handling the tape cassette, it is possible, although rare, that the ink ribbon can be drawn out along with the film tape and adhesive backing. In this case, the ink ribbon can adhere to the adhesive backing, ruining the tape cassette.
The ink ribbon is typically quite fragile. If the ink ribbon is the same width as the film tape, then when many characters or images are continuously printed, the ink ribbon can be weakened by heat or the removal of material across its entire width. This is especially true when printing in "negative"; that is, printing such that ink is transferred to form a surrounding dark background around character shapes while leaving the actual character shapes without ink, resulting in the appearance of light characters on a dark background. If the ribbon is sufficiently weakened, it can break easily.
The film tape and adhesive backing are typically almost exactly the same width, and are difficult to align. Ideally, the film tape and adhesive backing should be perfectly laminated, but especially when a provision is included for a wider ribbon than the film tape, alignment in the width direction is difficult to accomplish due to the various differing widths. Conventionally, between the printing head and the laminating or feed roller, adequate provision for alignment is not made.